1. Field of the Invention
The present invention relates to an acoustic wave contact detecting apparatus, such as an ultrasonic touch panel.
2. Description of the Related Art
Ultrasonic acoustic wave contact detecting apparatuses are in widespread use. Examples of their applications include operating screens of personal computers, ticket dispensers at train stations, copiers installed in convenience stores, and ATM's at financial institutions. These acoustic wave contact detecting apparatuses utilize transducers, including piezoelectric vibrators (piezoelectric elements) provided on a substrate (touch panel) formed of glass or the like. These transducers function both as generating means for bulk waves and as sensors for detecting acoustic waves which are scattered by a finger or the like that contacts the touch panel. The surface acoustic waves are scattered by a finger or the like. The scattering of the surface acoustic waves is detected by detection means. The detected signal is referenced against a clock signal of a controller, and the position at which the surface acoustic waves are scattered is determined.
Ultrasonic vibrations, which are generated as bulk waves, are converted to surface acoustic waves by acoustic wave generating means, and are propagated along the substrate.
When the bulk waves are converted to surface acoustic waves by the acoustic wave generating means, not all of the bulk waves are converted. Spurious waves, including unconverted bulk waves, surface acoustic waves which have passed through a reflection array, and surface acoustic waves which are reflected in directions other than predetermined directions, are generated. If these spurious waves are reflected along the substrate and reach the sensor side converters, they cause these converters to vibrate and generate voltages. These voltages are received as noise, and throw off proper judgment by the controller.
For this reason, vibration insulating or vibration absorbing materials are provided on the substrate to absorb the generated spurious waves (disclosed, for example, in Japanese Unexamined Patent Publication Nos. 6 (1994)-324792 (page 2, FIG. 1) and 61 (1986)-239322 (page 11, FIG. 2)). These vibration insulating and vibration absorbing materials are normally in the form of resin tape, which is adhesively attached to the substrate. The spurious waves which reach the tape are absorbed and attenuated.
In the conventional art, it is necessary to adhesively attach the vibration insulation or vibration absorbing member to the substrate. The adhesive attachment operation is manually performed, therefore increasing the manufacturing steps and reducing productivity. As a result, there is a problem that manufacturing costs are increased.